Hair consists of many long, parallel chains of amino acids. These chains, or polymers, of amino acids are bound to each other via 1) hydrogen bonding, 2) salt bridges between acid and base groups, and 3) disulfide bonds.
At alkaline pH, the disulfide bonds in hair can be broken (Dombrink et al., Chem Matters, 1983, page 8). For example, lye-based relaxers contain hydroxide ions which attack the disulfide linkages. The disruption of disulfide bonds by the lye-based relaxer is used to achieve straightening of the hair through changing of the relative positions of opposing polypeptide chains. The straightening process is completed by rinsing the hair and/or application of a neutralizing composition.
While lye and other alkali-based relaxers are highly effective at relaxing and straightening hair they can result in reduction of hair strength and potential loss of hair through breakage. Relaxing hair can therefore be viewed as a destructive and irritating process which can strip hair of its natural fatty acids. Exposing hair to alkaline conditions also damages the hair and further causes the cuticle or outer surface of the hair strands to become roughened and can result in ruffled, tangled, and generally unmanageable hair. Roughened hair catches light unevenly and makes the hair look lusterless and dull. The hair can also be left with increased levels of static upon drying, which can interfere with combing and result in a condition commonly referred to as “fly-away hair.”
A variety of approaches have been developed to alleviate these problems, including post-shampoo application of hair conditioners, such as leave-on and rinse-off products. Typically, conditioning rinses put back the oily coating, especially to the damaged portion of the hair where the cuticle has become ruffled since conditioners cling best to these portions. However, too much or too heavy a conditioner will make the hair stickier, thus attracting dirt and often may make more shampooing treatments necessary.
Yet another issue with the use of lye and other alkali-based hair relaxers is that their application leads to completely relaxed and straightened hair without any level of curl and/or any controllably retained level of curl. Furthermore, due to the reduction of hair strength and potential loss of hair due to breakage from such relaxing processes, any further application of a permanent wave process (i.e., to introduce a controlled amount of curl) to the already relaxed and straightened hair would be inadvisable as it would result in further damage and/or breakage of the hair.
Thus, there is a need for hair formulations and treatments that can provide improved conditioning benefit for hair relaxed with lye or alkali-based relaxers. Specifically, there is a need to provide long lasting moisturized feel, smooth feel, and manageability control to the treated hair when it is dried.
There is also a need for hair formulations and treatments that repair and/or strengthen damaged hair treated with lye or alkali-based relaxing agents or hydroxide-containing relaxing agents.
There is also a need for hair formulations and treatments that afford the ability to tune or select the level of curl achieved and/or retained in hair which has been relaxed with lye or alkali-based relaxing agents or hydroxide-containing relaxing agents.
Therefore, it is an object of this invention to provide improved compositions and methods for repairing and/or strengthening hair treated with lye or alkali-based relaxing agents or hydroxide-containing relaxing agents.
It is a further object of this invention to provide compositions and methods which can be used to tune or select the level of curl achieved and/or retained in hair that has been treated with lye or alkali-based relaxing agents or hydroxide-containing relaxing agents.